Problem

When running gh-aw workflows on GitHub Enterprise Cloud (GHEC) tenants (e.g., company.ghe.com), the Copilot CLI fails to authenticate because the API proxy / firewall does not correctly handle the token exchange flow for enterprise environments.

Relates to: github/gh-aw#18480

Symptoms

Two independent GHEC users (@kbreit-insight on myorg.ghe.com, @charleshancoder on xyz.ghe.com) report the same failure pattern:

1. Token exchange returns 403 on GHES API: POST https://api.{tenant}.ghe.com/copilot_internal/v2/token returns "Resource not accessible by personal access token" (403) when using a fine-grained PAT with Copilot Requests permission.

2. Copilot CLI sees "Error loading models: 400 Bad Request" when running inside the awf container, even though COPILOT_API_URL is set to the api-proxy address (http://172.30.0.30:10002).

3. GHEC domains not injected into --allowed-domains: The firewall blocks connections to {tenant}.ghe.com because the domain is not being automatically added to the allowed list. User reports: "When the firewall blocked a connection to GHE it showed a list of blocked and allowed domains. This also means the domain isn't being injected into the --allowed-domains argument."

4. Direct host test works differently: Running copilot --prompt directly on the host (bypassing awf/api-proxy) also fails with a 401 on user login, but the error path is different, suggesting the api-proxy is transforming or misrouting the request.

Diagnostic Evidence

Both users ran the same diagnostic script. Key findings:

Test 1: COPILOT_GITHUB_TOKEN → GHES token exchange
  URL: https://api.{tenant}.ghe.com/copilot_internal/v2/token
  Status: 403  ("Resource not accessible by personal access token")

Test 2: github.token (Actions) → GHES token exchange  
  URL: https://api.{tenant}.ghe.com/copilot_internal/v2/token
  Status: 403  ("Resource not accessible by integration")

Test 3: COPILOT_GITHUB_TOKEN → api.github.com token exchange
  Status: 401  ("Bad credentials")  ← expected: GHEC PAT invalid on github.com

Test 4: GHES endpoint availability
  /copilot_internal/v2/token → 403
  /copilot_internal/v2/models → 404
  /models → 404
  /meta → 200

Agent logs inside awf container:
  Using COPILOT_API_URL from environment: http://172.30.0.30:10002
  Error loading models: Error: Failed to list models: 400 Bad Request

Root Causes (suspected)

There appear to be two distinct issues:

Issue 1: GHEC domains not added to firewall allowed list

When GITHUB_SERVER_URL is a GHEC tenant (e.g., https://company.ghe.com), the firewall's --allowed-domains argument does not automatically include:

• company.ghe.com
• api.company.ghe.com
• *.company.ghe.com (for any subdomains the GHEC tenant uses)

Expected: The firewall should detect non-github.com GITHUB_SERVER_URL values and automatically add the GHEC domain and its API subdomain to the allowed list.

Issue 2: API proxy does not route Copilot token exchange to GHES endpoint

The api-proxy intercepts Copilot CLI's token exchange request but may be routing it to api.github.com/copilot_internal/v2/token instead of api.{tenant}.ghe.com/copilot_internal/v2/token. This would explain:

• The 400 Bad Request from the api-proxy (it proxied to the wrong host)
• The fact that previously (v0.45.0) users could work around this by manually setting GITHUB_SERVER_URL and GITHUB_API_URL env vars in the lock file

The api-proxy needs to respect GITHUB_API_URL / GITHUB_SERVER_URL when determining the upstream Copilot API endpoint for token exchange and model listing.

Proposed Fix

1. Firewall: Auto-detect GHEC domains from GITHUB_SERVER_URL environment variable and add them to --allowed-domains. When GITHUB_SERVER_URL is not https://github.com, extract the host and add both {host} and api.{host} (or derive from GITHUB_API_URL).

2. API Proxy: When proxying Copilot API requests (token exchange, model listing), use GITHUB_API_URL as the upstream base URL instead of hardcoding api.github.com. The environment variables GITHUB_SERVER_URL and GITHUB_API_URL are already passed through to the awf container by gh-aw.

Environment Details

• gh-aw version: v0.58.0 (latest at time of testing)
• Firewall version: 0.24.1 (also tested with latest)
• GHEC tenants: Two independent organizations on *.ghe.com
• PAT type: Fine-grained with Copilot Requests permission
• Previous working version: gh-aw v0.45.0 (with manual lock file edits)